General Misc > Misc

My robot progress thread...

(1/5) > >>

Nyx:
Hello,

I posted here several months ago about my robot building project. Well, I'm starting to plan it some more. I will be completing it during the summer. Basically, it's going to be a mobile robot. The goal is to experiment with vision. As such, I plan on using my laptop (running linux) to do the processing, as it will offer alot of power (It's a Core Duo T2500, dual core, with 1 GB RAM). The laptop also has the nice benefit of offering me wifi access, which will allow easy remote control, as well as remote development directly on the robot, through my desktop.

I plan on doing things simple. I have no metal working tools, so I will build it out of wood. The base will essentially be made of wood circles (about 18 inches in diameter and 1 inch thick) stacked and linked together by little wood poles (so the assembly will have multiple stages). I plan to have one level for the motor, battery and power management systems (most likely a deep cycle marine battery, about 30 pounds, ~30-40AH, 12V). One stage for the control circuits (USB phidget interface board, relays, etc). One stage for my laptop, and a final top level, above which will be a mast, atop which will be the "head of the robots", containing two webcams, for stereoscopic vision. The movement will be done with two wheels attached to two independent motors (differential drive). The robot will have its components exposed. I think wood might look odd to a few people, but it should actually look OK.

I might also attempt to build an arm later on, but the main goal of the robot will be to explore and map the environment, as well as recognize people, map objects, etc. The robot will include *no* sensors other than the cameras. No range finders, no accelerometers, no sonars. The goal is really to base everything on vision processing. I don't plan on having pan and tilt for the cameras. I'm thinking that the robot can simply rotate to view things around. I will put the camera high enough (say, 4.5'), so that the robot can easily people, obstacles, and the ground in front of it.

What I have bought so far:
- The laptop (Core Duo T2500, 1GB RAM)
- Ubuntu linux, server config, console only (hey, it's free)
- Two motors, wormgear drive, 108 RPM, 12V, 4A
- A 175W inverter to power the laptop (to avoid wasting its battery)
- Diodes, voltage regulators, breakers, switches to build power distribution circuits
- A few bosch 12V/20A relays
- A 4 port USB 2.0 hub (unpowered)
- 0-15V 25A variable regulated DC power supply (to test parts, power robot, charge battery)

What I still need:
- A marine deep cycle battery, 30+ AH
- Wires, shrink wrap, metal casings for parts
- Wooden base and wooden poles (my mom will make those for me, heheh, no joke)
- 6" wheels and rotating caster wheels
- Two USB 2.0 640x480 webcams that with with linux (with full USB 2.0 speed)
- A phidget USB 0/16/16 interface board
- Some 3000+ uF 25V+ electrolytic capacitors for mypower assembly
- 5/6V and 16V power regulators
- Pieces to build a robot arm (still being designed)

I might actually need more,but this is a minimum. I will buy things as I get the money, basically. I don't really plan on using any microcontrollers, servos, or parts designed specifically for robotics.

I'm pretty confident that I can make this work, but feedback, comments, support and hardware donations are always welcome ;)

Edit: Just ordered two Quickcam Notebook Pro 1.3MP, USB 2.0. They are supported under linux with the UVC driver. Also have a built-in microphone. So that pretty much settles the vision hardware part ;)

Nyx:
Soo, yeah, I ordered two USB 2.0 webcams... Refurbished, but they seem to be of very good quality. 1.3 MP each (not SW enhanced), made for notebooks. I got them for $50 each, shipping included. I also bought two windshield wiper motors, and alot of parts destined to build my power regulation circuit.

I'm not a pro at electronics, so I'm going to go simple. I will simply hook the motors using relays, so in an on/off configuration. Perhaps I will have two speeds, to allow for more precise movements when needed. I want to build some kind of circuitry so that when both the forward and reverse relays are turned on, the thing doesn't short. I don't know what's the easiest way to go about this, perhaps just having one relay turn off the other... Perhaps just programming it so that doesn't happen, and having some breakers in place to avoid anything bad.

I had a friend who might have been able to help me. He is a mechanical engineer and had access to some metal cutting equipment. Unfortunately, the guy is maniaco depressive, on medication, and very unstable... Last time I spoke to him he was yet again telling me about 911 conspiracy videos, and how the US government is out to get us, even though we both live in Canada. Sooo..... I'm going to have to revert to my wood building project. It doesn't really matter that much, since this robot is really meant as a vision experiment platform. Perhaps I can build a prettier robot later, if I can get some help.

As I said, my mom (!) is going to cut wood pieces for me, according to a plan. She works in a place where they build/repair/restore furniture, and she's offered to help... So I will be able to get some good quality wood parts... And give my robot a nice antique finish :P

One of my main problems is that i'm not well equipped to fix the motor to a wheel, and to fix the motor to the chassis. The motor has its screw-holes on the front, where the axle comes out to attach the wheel.... In the worst case, I might make a hole in a wood block, stick the motor in it, and fill the hole with glue (yes, I know, how ghetto eh?). I guess the best strategy would be to find some kind of metal bracket of the exact right shape and drill holes in it... But even there, the bracket would need to have a strange shape. Like I said, I'm also not sure how to attach the wheel to it. I'm going to see if I can find some wheels that have a hole exactly the diameter of the axle, which I could also solidly glue in place, if that's possible. This is actually the most complex part of the assembly process of my robot.... Building the motor-wheel assembly and attaching that solidly enough to the platform so that everything doesn't just fall apart.

JonHylands:
Nyx,

Where abouts in Canada are you? I live a couple hours west of Toronto, and have a Sherline milliing machine/lathe setup, so I can machine small parts (like axle-wheel hubs) from brass/aluminum/plastic.

If you have some cash to spend on this, I would strongly recommend you get a commercial, serial-controlled motor speed controller. There are any number of places that sell them, depending on how much current you need to push...

- Jon

Nyx:

--- Quote from: JonHylands on February 08, 2007, 02:54:58 PM ---Nyx,

Where abouts in Canada are you? I live a couple hours west of Toronto, and have a Sherline milliing machine/lathe setup, so I can machine small parts (like axle-wheel hubs) from brass/aluminum/plastic.

If you have some cash to spend on this, I would strongly recommend you get a commercial, serial-controlled motor speed controller. There are any number of places that sell them, depending on how much current you need to push...

- Jon


--- End quote ---

I live in montreal. I might have money to spend, if the prices are reasonable ;)

As far as motor controllers... I would need something I can directly hook to a PC, and that can be used on linux. I also need it to support up to 6 amps per motor, at 12V.

JonHylands:
http://www.dimensionengineering.com/Sabertooth2X10.htm

You will need either a serial transceiver chip or a USB -> TTL converter.

USB: http://www.sparkfun.com/commerce/product_info.php?products_id=198

I don't know where you would get a serial converter (max232), but there are a ton of places that sell them.

- Jon

Navigation

[0] Message Index

[#] Next page

Go to full version